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Objectives To understand persistence of the virus in body fluids and immune response of infected host to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), an agent of coronavirus disease 2019 (COVID-19). Methods We determined the kinetics of viral load in several body fluids through real time reverse transcription polymerase chain reaction (rRT-PCR), serum antibodies of IgA, IgG and IgM by enzyme linked immunosorbent assay (ELISA), and neutralizing antibodies by microneutralization assay in 35 COVID-19 cases from two hospitals in Guangdong, China. Results We found higher viral loads and prolonged shedding of virus RNA in severe cases of COVID-19 in nasopharyngeal (1.3×10 6 vs 6.4×10 4 , p<0.05; 7∼8w) and throat (6.9×10 6 vs 2.9×10 5 , p<0.05; 4∼5w), while comparable in sputum samples (5.5×10 6 vs 0.9×10 6 , p<0.05; 4∼5w). Viraemia was rarely detected (2.8%, n=1/35). We detected early seroconversion of IgA and IgG at 1 st week after illness onset (day 5, 5.7%, n=2/35). Neutralizing antibodies were produced in the second week, and observed in all 35 included cases after 3 rd week illness onset. The levels of neutralizing antibodies correlated with IgG (r s =0.85, p<0.05; kappa=0.85) and IgA (r s =0.64, p<0.05; kappa=0.61) in severe, but not mild cases (IgG, r s =0.42, kappa=0.33; IgA, r s =0.32, kappa=0.22). No correlation with IgM in either severe (r s =0.17, kappa=0.06) or mild cases (r s =0.27, kappa=0.15) was found. Conclusions We revealed a prolonged shedding of virus RNA in upper respiratory tract, and evaluated the consistency production of IgG, IgA, IgM and neutralizing antibodies in COVID-19 cases.

BackgroundGuangdong is a hyperepidemic area of dengue, which has over 0.72 million cumulative cases within the last four decades, accounting for more than 90% of cases in China. The local epidemic of dengue in Guangdong is suspected to be triggered by imported cases and results in consequent seasonal transmission. However, the comprehensive epidemiological characteristics of dengue in Guangdong are still unclear.MethodsThe epidemiology, seroprevalence, molecular evolution of dengue virus, and the development of policies and strategies on the prevention and control of dengue were analyzed in Guangdong, China from 1978 to 2017.FindingsSeasonal transmission of dengue virus in Guangdong, China was mainly sustained from July to October of each year. August to September was the highest risk period of local dengue outbreaks. Most of the dengue cases in Guangdong were young and middle-aged adults. Five hundred and three fatal cases were recorded, which declined within the last two decades (n = 10). The serological test of healthy donors' serum samples showed a positive rate of 5.77%. Dengue virus 1–4 (DENV 1–4) was detected in Guangdong from 1978 to 2017. DENV 1 was the dominant serotype of dengue outbreaks from 1978 to 2017, with an increasing tendency of DENV 2 since 2010. Local outbreaks of DENV 3 were rare. DENV 4 was only encountered in imported cases in Guangdong, China. The imported cases were the main source of outbreaks of DENV 1–2. Early detection, management of dengue cases, and precise vector control were the key strategies for local dengue prevention and control in Guangdong, China.InterpretationDengue has not become an endemic arboviral disease in Guangdong, China. Early detection, case management, and implementation of precise control strategies are key findings for preventing local dengue transmission, which may serve for countries still struggling to combat imported dengue in the west pacific areas.

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